The question https://christianity.stackexchange.com/questions/35704/to-what-point-in-time-can-the-bible-be-proven-accurate made me wonder: Is the common interpretation of 1 Nephi 13:26-28 that something was physically omitted from scripture? I am aware of the Joseph Smith Translation, but is the point to bring back physically removed parts? In at least one instance I know of, the "translation" is just a commentary, with no changed text, that makes it clear what is meant. This makes me wonder whether the goal was a corrected understanding, not so much a corrected text.
An other interpretation I can come up with is that, without requiring much change to scripture, doctrines that are introduced (e.g. Trinity) became basis for further theology, scripture translation (translation is always also in part interpretation) and so on. That also "[take] away from the gospel of the Lamb many parts which are plain and most precious".
So, is the official position as of now that there were things physically omitted from scripture, or that the cause is rather false doctrines themselves that became the spiritual basis for later generations? Or is there no "official" interpretation?